DESCRIPTION: (Adapted from the application) The ability to measure the number and activity of beta-adrenergic receptors would be of value in the evaluation of heart disease and its treatment. The proposed work will focus on the development of high-affinity beta receptor ligands chosen for their expected capacity to yield good quality positron tomographic (PET) data. These will be labeled with carbon-11 and fluorine-18 using a general and efficient branching approach. The specific receptor binding of these ligands will be measured in mice and pigs, and imaging experiments will be performed in pigs. This work will provide the needed data for obtaining approval for future use of these tracers in human subjects. This work will also include kinetic analysis to determine the feasibility of using these ligands for quantitative receptor determinations in the heart. If beta receptor quantitation proves to be feasible, the investigators will perform quantitative PET receptor measurements in vivo and compare these with in-vitro determinations using the same tissue.